<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        class Father {
            constructor(x, y) {
                this.x = x;
                this.y = y;
            }
            sum () {
                console.log(this.x + this.y);
            }
        }
        class Son extends Father {
            constructor (x, y) {
                super(x, y);
                this.x = x;
                this.y = y;
            }
            subtract () {
                console.log(this.x - this.y);
            }
        }
        const son = new Son (1, 2);
        son.sum();
        son.subtract();
    </script>
</body>
</html>